Department nsportation al Aviation nistration Advisory Circular ct: Laser Airworthiness Installation nce Date: 12/15/14 Initiated By: AIR-134 AC No: 20-183
U.S.
of Tra Feder Admi
Subje Guida
1 PURPOSE.
1.1 In this advisory circular (AC), we recommend one way to obtain Federal Aviation Administration (FAA) airworthiness approval for the installation of aircraft-mounted, nonrequired, invisible spectrum laser equipment such as infrared surveillance laser and light detection and ranging (LIDAR) equipment. This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, to comply with the requirements found in Title 14 of the Code of Federal Regulations (14 CFR) 23.1301, 23.1309, 23.1529, 23.1581, 25.1301, 25.1309, 25.1529, 25.1581,
27.1301, 27.1309, 27.1529, 27.1581, 29.1301, 29.1309, 29.1529, and 29.1581 for the laser equipment aspects only. If you use the means described in this AC, you must follow it in its entirety.
1.2 This AC only addresses unique laser airworthiness installation requirements. It is not comprehensive installation guidance for airborne equipment with lasers because it does not address all the applicable installation airworthiness requirements such as those discussed in paragraph 7 below.
1.3 This AC is not intended for installations seeking airworthiness approval of required aircraft equipment that has a laser with radiation contained within a protective housing (for example, a ring laser gyro).
1.4 This AC is not intended for laser-based weapons and aircraft self-protection countermeasures equipment installations.
1.5 This AC is only intended for invisible lasers. This AC does not apply to visible lasers because they pose additional hazards (such as flash blindness) that are not addressed in this AC.
1.6 Additional airworthiness certification criteria beyond what is described in this AC would be required for installations intended for laser operation with head- or helmet-mounted vision devices such as night vision goggles (NVG). For NVG
1.7 guidance, refer to AC 27.1, Certification of Normal Category Rotorcraft, miscellaneous guidance (MG) 16, or AC 29.2, Certification of Transport Category Rotorcraft, MG 16.
2 AUDIENCE.
We wrote this AC for aircraft manufacturers, laser equipment manufacturers, installation shops, and other applicants seeking FAA airworthiness approval of invisible spectrum laser equipment installations on part 23, 25, 27, and 29 aircraft.
The airworthiness approval can occur under a type certificate (TC), supplemental type certificate (STC), amended type certificate (ATC), amended supplemental type certificate (ASTC) or data approval for major alteration. This AC also provides guidance to FAA personnel involved in a TC, STC, ATC, ASTC, or data approval for major alterations that install invisible spectrum laser equipment.
3 BACKGROUND.
3.1 Laser Surveillance Equipment.
Local, State, and Federal law enforcement agencies use forward looking infrared (FLIR) equipment with laser illuminators, pointers, and range finders for nighttime, covert surveillance. Laser surveillance equipment may be used to support several kinds of tasks and missions, varying from target range-finding to illuminating small spots or large areas. Certification of such airborne surveillance equipment installations with lasers presents some unique challenges because lasers can pose a potential eye hazard to flight crew, passengers, other aircraft occupants, and the nonflying public. Laser surveillance equipment typically uses class IIIb or IV lasers. Before this guidance, many surveillance systems were installed using an STC for laser surveillance equipment that only included provisional wiring for the laser. For these installations, the STC type design would show that the laser was electrically disabled. These installations may have not completely addressed all the laser hazards.
3.2 LIDAR.
A LIDAR uses a laser to perform ranging by measuring the reflected return of a projected laser beam. LIDAR devices can be used in mapping terrain elevation, obstacles, and vegetation; or atmospheric measuring (for example, particulate tracking or turbulence monitoring). Some LIDARs use an internal class IIIb or IV laser, and through an internal mechanism, diffuse the external laser emissions to a class I level.
LIDAR external laser emissions can range from class I to class IV.
3.3 Eye Hazard.
FLIR and LIDAR lasers can be especially hazardous because the beam is invisible and there is no blink reflex reaction to protect the eye, so eye exposure may initially go undetected. Exposure to lasers operating within the 750 to 1,400 nanometer (nm) near infrared spectrum can cause retinal eye damage. The 400 to 1,400 nm wave band is known as the retinal hazard region. Laser equipment that operates in the 315 to 400 nm ultraviolet or the 1,400 to 10,600 nm far infrared spectrums can damage the cornea,
3 lens, or both. Most FLIR and LIDAR lasers operate with a wavelength of 800 to 1570 nm. The extent of eye damage depends on the laser exposure dose.
4 ROLES AND RESPONSIBILITIES.
4.1 FAA Regulatory Authority Role.
The FAA is responsible for issuing a design approval (such as an STC) or other data approval for an aircraft laser installation when an applicant demonstrates the laser installation meets the applicable airworthiness requirements.
4.2 Food and Drug Administration (FDA) Regulatory Authority Role.
The FDA has the authority to regulate light-emitting products and electronic product radiation (Title 21 of the United States Code section 360ii, Program of control). The FDA is also responsible for approval or disapproval of variance applications for a laser not meeting the laser performance standards found in Title 21 of the Code Federal Regulations (21 CFR) part 1040, Performance Standards for Light-Emitting Products.
4.3 Laser Manufacturer Equipment Certification Role.
The laser manufacturer is responsible for self-certifying that the laser meets the performance standards in § 1040.10, Laser products, and obtaining a variance from the FDA when laser equipment does not meet a laser performance standard.
4.4 Installation Applicant Role.
The applicant who applies for an installation design approval is responsible for meeting all applicable FAA airworthiness and FDA laser performance and variance requirements.
5 DEFINITIONS.
5.1 Accessible Emission Limit (AEL).
The maximum accessible emission level permitted by the FDA within a particular laser hazard class as stated in § 1040.10(c), (d), and (e).
5.2 Divergence.
The increase in diameter of the laser beam with distance from the exit aperture.
Divergence is an angular measurement of the beam spread, expressed in milliradians (mrad) defined at the points where the irradiance is 37 percent of the peak irradiance.
5.3 Irradiance.
A means of expressing power of the beam per unit area, which is expressed in watts per centimeter squared (W/cm2).
5.4 Maximum Permissible Exposure (MPE).
The level of laser radiation to which an unprotected person may be exposed without hazardous effect or adverse biological change in the eye or skin, normally expressed in milliwatts per centimeter squared (mW/cm2) or millijoules per centimeter squared (mJ/cm2).
5.5 Nominal Ocular Hazard Distance (NOHD).
The distance from the laser beyond which the laser radiation does not exceed the MPE.
5.6 Specular Reflection.
A mirror-like deviation of radiation (light) following incidence on a surface.
6 LASER CLASSES.
The FDA recognizes four major hazard classes (I to IV) of lasers, including three subclasses (IIa, IIIa, and IIIb) as shown in the table below. International Electrotechnical Commission (IEC) equivalent laser classes are included in table 1 for products labeled under the classification system of the IEC.
Table 1. Laser Classes and Product Hazard Class FDA Class IEC Laser Product Hazard I I, IM Considered nonhazardous. Hazard increases if viewed with optical aids, including magnifiers, binoculars, or telescopes.
IIa, II 2, 2M Hazard increases when viewed directly for long periods of time.
Hazard increases if viewed with optical aids.
IIIa 3R Depending on power and beam area, can be momentarily hazardous when directly viewed or when staring directly at the beam with an unaided eye. Risk of injury increases when viewed with optical aids.
IIIb 3B I mmediate skin hazard from direct beam and immediate eye hazard when viewed directly.
IV 4 Immediate skin hazard and eye hazard from exposure to either the direct or reflected beam; may also present a fire hazard.
7 LASER EQUIPMENT INSTALLATION GUIDANCE.
This section provides installation guidance for the laser aspects of equipment with invisible wavelength lasers. In addition to this specific laser installation guidance, the
5 installation must meet all other applicable airworthiness requirements such as those involving electrical system capacity, electrical circuit protection, lightning direct effects, ice protection, flammability, environmental qualification (such as radiated emissions, crash safety, vibration, and temperature), changes to flight and handling characteristics (such as drag, stall, max and min air speeds, and trim), vibration, structures, static and pitot systems, and electrical wiring interconnection systems. Laser equipment installations typically follow three basic steps: (1) laser equipment manufacturer certification of the laser equipment, (2) FDA review and approval of variance, and (3) FAA laser equipment installation approval. A fourth step to recertify the laser equipment may be required if the installer modifies the laser or deviates from an FDA variance. Step 2 would not be required for installations of FDA class I lasers or IEC class 1, 2, and 3R lasers.
7.1 Laser Equipment Certification.
Laser equipment installers must install the equipment according to the manufacturer’s specifications as certified by the manufacturer to the FDA. Before installing the laser equipment, the installer must comply with all applicable FDA 21 CFR requirements (such as §§ 1002.10, 1010.2, 1010.3, 1040.10, and 1040.11) and have a label or tag permanently affixed to, or inscribed on, the laser equipment certifying the equipment complies with performance standards for laser products under part 1040. If this label or tag specifies an FDA variance, the type design for the installation must show that the variance’s technical controls applicable to the installation (such as aircraft interface safety interlock) have been satisfied.
7.2 FDA Variance.
According to the FDA, surveillance lasers and LIDAR systems are considered “surveying, leveling, and alignment laser products,” which are specific purpose laser products described in § 1040.11(b) and limited to class I AEL for the invisible laser wavelengths. However, most airborne surveillance lasers and some LIDARs exceed the allowable class I AELs for the invisible wavelengths and therefore require variances as described in § 1010.4. For products labeled under the classification system of the IEC, classes 1, 2, and 3R are acceptable class limits for an invisible emission and therefore do not require a variance. The FDA variance may require administrative controls (for example, the laser equipment purchasing organization is to maintain an active program of training for its employees in the safe use of the laser system) and technical controls (such as a range finder cutoff that disables the laser when the distance between the laser’s aperture and the object being exposed is less than the NOHD).
7.3 Aircraft Laser Equipment Installation.
7.3.1 System Safety Analysis.
You must perform a system safety analysis to assess whether the installed laser equipment meets 14 CFR 23.1309, 25.1309, 27.1309, or 29.1309. Refer to AC 23.1309-1, System Safety Analysis and Assessment for Part 23 Airplanes. For part 25 airplanes, refer to AC 25.1309-1, System Design and Analysis. For part 27 rotorcraft, refer to AC 27.1309, Equipment, Systems and Installations. For part 29
6 rotorcraft, refer to AC 29.1309, Equipment, Systems and Installations. The systems safety assessment should address the following:
7.3.1.1 Laser Equipment Malfunction.
Laser equipment malfunction resulting in an aircraft crewmember’s or passenger’s eye or skin being exposed to invisible laser radiation exceeding the MPE is considered no less than a hazardous functional failure condition and could be catastrophic if continued safe flight is not possible because of the severity of the laser damage to a pilot’s eye or skin. In your system safety assessment, you should document the rationale for a hazardous functional failure condition classification. If there is no direct or reflected path into the cockpit or cabin because of the location of the laser and physical shielding provided by the aircraft structure, this failure condition does not apply.
7.3.1.2 System Safety Considerations.
In assessing the failure conditions, you should consider direct and reflected radiation; the location of the laser, laser beam steering mechanism, and circuitry; the use of mechanical, software, or airborne electronic hardware (AEH) stops that prevent the laser from being steered in a direction that could result in the aircraft occupants’ eyes being exposed to direct or reflected radiation; laser arming and firing circuitry;
and other design features whose malfunction could contribute to an inadvertent exposure or an exposure that exceeds the MPE (such as failure of the internal laser diffuser used to reduce the AEL). If the laser’s steering stops are implemented in software or AEH, their assurance level should be commensurate with the functional failure condition associated with the stops. Reflections off any part of the aircraft (such as the structure, blades, skids, or landing gear) should be considered specular.
7.3.1.3 Aircraft Structure.
Any malfunction resulting in damage to aircraft structure due to laser exposure should be assessed to determine the extent of aircraft damage and the associated functional failure condition classification.
7.3.1.4 Equipment Interfaces.
Any malfunction of the laser equipment’s interfaces with other aircraft system will have to be assessed to determine the effect on the aircraft system and laser equipment as well as the associated functional failure condition classifications.
7.3.1.5 Other Functional Failure Condition.
Other malfunctions not described in paragraphs 7.3.1.1 through 7.3.1.4 of this AC should be identified and assessed to determine their functional failure conditions.
7.3.1.6 Loss of Function.
Because the laser is nonrequired equipment, the functional failure condition for loss of the laser function is “no effect.”
7.3.2 NOHD and MPE Calculations.
You should provide a report that documents how the NOHD and MPE were calculated to include all equations, references for those equations, table references, equation parameters (such as wavelength, divergence, exposure time, and power), dimensions for the reflected and direct radiation paths into aircraft’s windows, and justification for the exposure duration. For laser illuminators, spotters, range finders, and other nonscanning lasers, the NOHD exposure duration should be based on the maximum exposure duration expected, but not less than 10 seconds. AC 70-1, Outdoor Laser Operations, and American National Standards Institute document ANSI Z136.1, American National Standard for Safe Use of Lasers, provide acceptable means to calculate MPE and NOHD.
7.3.3 Installation Type Design.
The installation type design must include all the 21 CFR 1040 requirements that would be applicable to the installation (such as the key control, emissions indicator, labels, and remote interlock connector) and the technical controls (such as the aircraft interface safety interlock) from the FDA variance that affect the aircraft installation.
7.3.4 Software.
If the laser equipment includes software that can contribute to malfunctions described in paragraph 7.3.1 above, develop the software using the guidance in AC 20-115C, Airborne Software Assurance, to a software level commensurate with the functional failure condition classifications determined from paragraph 7.3.1.
7.3.5 AEH.
If the laser equipment includes custom AEH (such as an application-specific integrated circuit, field programmable logic device, or programmable logic device), which can contribute to the malfunctions described in paragraph 7.3.1 above, develop the AEH using RTCA, Inc., document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware, to a design assurance level commensurate with the functional failure condition classifications determined from paragraph 7.3.1. For custom AEH classified as simple, paragraph 1.6 of RTCA/DO-254 applies.
Note: We encourage the use of industry-recognized system safety standards (such as SAE International ARP 4761 and IEC 61508) and development assurance standards (such as RTCA/DO-178C, RTCA/DO-254, and IEC 61508) for the laser equipment when its malfunction could result in an exposure that could exceed the MPE for people outside the laser-equipped aircraft.
7.3.6 Configuration Control.
Unapproved changes to the laser equipment or the installation should not be made because they could affect the airworthiness (for example, electromagnetic and
8 environmental compatibility or new failure modes) of the equipment installation and invalidate the laser equipment certification and FDA-approved variances. The applicant should provide a plan for maintaining configuration throughout the product life cycle.
If the installation results in a modification to the laser equipment as certified by the laser equipment manufacturer, the laser equipment must be recertified as described in § 1040.10(i).
7.3.7 Aircraft Flight Manual Supplement (AFMS).
An approved AFMS is required for laser equipment installation where airframe limitations, operational procedures, or the flight characteristics of the basic aircraft change because of the proposed modification. It should include any special procedures required for safe operation of the laser system. It must also include any changes to the limitations of the aircraft caused by the installation, particularly for externally mounted systems. AC 70-1 should be consulted for additional requirements and permits.
7.3.7.1 For the laser equipment installation, the AFMS must include the following limitations:
7.3.7.1.1 The laser must not be used to intentionally radiate other flying aircraft.
7.3.7.1.2 The laser must not be used on the ground or during taxi, takeoff, or landing. For FDA class IIIb and IV lasers and IEC class 3B and 4 lasers, the key control must be in the off position on the ground and during taxi, takeoff, and landing.
7.3.7.1.3 The laser must not be used to radiate people when the distance between the laser and the people is less than the NOHD. The NOHD should be specified in the AFMS or on a placard.
7.3.7.1.4 The atmospheric conditions when the laser must not be used (such as rain or snow).
7.3.7.1.5 The flight conditions when the laser must not be used (such as angle of bank, flying in close proximity to terrain, or hoist operations).
7.3.7.1.6 The laser must not be used if any of the laser safety interlocks that require an interface to an aircraft system are inoperable. The AFMS should identify the aircraft interface safety interlocks. An FDA variance could require an aircraft interface safety interlock (such as an interface with a radar altimeter that disables the laser when the aircraft height above the terrain is less than a specified altitude).
7.3.7.1.7 The aircraft configurations when the laser must not be used (such as when cargo mirrors are installed since they may provide a reflected path into the cockpit).
7.3.7.2 The AFMS must also contain the following user information identified in § 1040.10(h)(1):
7.3.7.2.1 Adequate instruction for operation, including warnings and cautions concerning precautions to avoid possible exposure to laser and collateral radiation above accessible limits.
7.3.7.2.2 Legible reproductions of all labels and hazard warnings required by §§ 1040.10(g) and 1040.11 to be affixed to the laser product.
7.3.7.2.3 A listing of all controls, adjustments, and normal, abnormal, and emergency procedures for operation including the following statement: “Caution—use of controls or adjustments or performance of procedures other than those specified herein may result in hazardous radiation exposure.”
7.3.8 Laser Safety Program.
We recommend that the aircraft operator establish a laser safety program in accordance with ANSI Z136.1, paragraph 1.3.
7.3.9 Instructions for Continued Airworthiness (ICA).
In addition to what is required by the airworthiness regulations, the ICA should contain the following laser service information:
7.3.9.1 Procedures for service with appropriate warnings and precautions to avoid exposure to laser and collateral radiation above the accessible emission limits,
7.3.9.2 A schedule of maintenance to maintain the product in compliance,
7.3.9.3 A listing of controls and procedures that could increase the level of accessible radiation,
7.3.9.4 Identification of removable portions of protective housings allowing human access to laser or collateral radiation above the accessible emission limits,
7.3.9.5 Procedures to avoid exposure to levels of laser and collateral radiation known to be hazardous for each procedure or sequence of maintenance procedures to be accomplished,
7.3.9.6 Reproductions of required labels (color optional) and warnings, and
7.3.9.7 Equipment location of the required labels and warnings.
7.3.10 STC Limitations.
The STC limitations must contain the FDA variance’s administrative controls that would limit the applicability of the STC (for example, government agencies only).
7.3.11 LIDAR Installations Appendix B identifies the section 7.3 paragraphs that should be applied to one example LIDAR installation configuration, provides recommendations for installations with multiple LIDAR equipment configurations, and provides the criteria for a LIDAR equipment change to be considered a minor change in type design or a minor alteration.
8 PUBLIC USE.
8.1 Most surveillance lasers were developed for public use operations and were not developed using FAA-recognized software assurance, system assurance, airborne electronic hardware assurance, and safety analysis process. As a result, they will most likely not meet the applicable airworthiness requirements. We recognize public aircraft, as defined in Title 49 of the United States Code sections 40102(a)(41) and 40125, are not required to meet FAA airworthiness requirements. However, if the public aircraft operator wishes to remain FAA compliant, the applicant must either (1) satisfy the guidance materials in paragraph 7 of this AC, or some acceptable alternative, or (2) the type design for the installation must show the laser feature is disabled. The following are the installation certification, maintenance, and flight manual requirements for a disabled laser:
8.1.1 The type design data must show the laser feature is disabled (for example, the arming and firing wiring harness connector is capped and stowed). The nonlaser features (such as FLIR) can be electrically enabled and operational.
8.1.2 Before operating the aircraft in operations other than public use, the laser features must be disabled through some maintenance action (such as removing a dongle or disconnecting, capping, and stowing a wiring harness).
8.1.3 The installed laser equipment should comply with all applicable 21 CFR requirements (such as §§ 1002.10, 1010.2, 1010.3, 1010.4, 1040.10, and 1040.11).
8.1.4 The ICA must include inspection instructions to verify the laser’s feature is disabled.
The procedures to transition from the FAA-approved civil use configuration to the modified public use configuration and back to the civil use configuration should be included in the ICA.
8.1.5 The ICA should contain maintenance procedures to protect the maintainers from laser hazards.
8.1.6 For TC or ATC installations, the limitation in the type certificate data sheet (TCDS) must state: “Laser operation is not FAA approved for civil aircraft operations. The laser is disabled.”
8.1.7 For STC or ASTC installations, the limitation in the “Limitations and Conditions” section must state: “Laser operation is not FAA approved for civil aircraft operations.
The laser is disabled.”
8.1.8 The flight manual supplement must include a limitation stating: “Laser features are not FAA approved for civil aircraft operations. These features are disabled.”
8.1.9 The following caution must be added to the flight manual supplement: “The FAA has not assessed all hazards associated with the laser feature(s) and the FAA has not validated the manufacturer’s laser safety or hazard assessments.”
8.1.10 A placard must be installed near the laser controls stating: “Laser operation is not FAA approved.”
9 APPLICABLE 14 CFR SECTIONS.
Refer to 14 CFR 23.1301, 23.1309, 23.1529, 23.1581, 25.1301, 25.1309, 25.1529,
25.1581, 27.1301, 27.1309, 27.1529, 27.1581, 29.1301, 29.1309, 29.1529, and 29.1581.
For part 23 aircraft, § 23.1301 may not be applicable.
10 APPLICABLE 21 CFR SECTIONS.
Refer to 21 CFR 1002.10, 1002.13, 1002.20, 1010.2, 1010.3, 1010.4 1040.10, and 1040.11.
If you have any suggestions for improvements or changes, you may use the template provided at the end of this AC.
Manager, Design, Manufacturing, & Airworthiness Division Aircraft Certification Service
Appendix A A-1 Appendix A. Related Documents A.
1 FEDERAL AVIATION ADMINISTRATION (FAA) ADVISORY CIRCULARS (AC).
A.1.1 AC 27-1B, Certification of Normal Category Rotorcraft.
A.1.2 AC 29-2C, Certification of Transport Category Rotorcraft.
A.1.3 AC 20-115C, Airborne Software Assurance.
A.1.4 AC 20-152, RTCA, Inc., Document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware.
A.1.5 AC 20-168, Certification Guidance for Installation of Non-Essential, Non-Required Aircraft Cabin Systems & Equipment (CS&E).
A.1.6 AC 20-171, Alternatives to RTCA/DO-178B for Software in Airborne Systems and Equipment.
A.1.7 AC 23.1309-1, System Safety Analysis and Assessment for Part 23 Airplanes.
A.1.8 AC 25.1309-1, System Design and Analysis.
A.1.9 AC 27.1309, Equipment, Systems, and Installations (included in AC 27-1B).
A.1.10 AC 29.1309, Equipment, Systems, and Installations (included in AC 29-2C).sure A.1.11 AC 70-1, Outdoor Laser Operations.
A.2 INDUSTRY STANDARDS.
A.2.1 SAE International (SAE) ARP4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment.
A.2.2 RTCA, Inc., document RTCA/DO-160G, Environmental Conditions and Test Procedures for Airborne Equipment.
A.2.3 RTCA/DO-178C, Software Considerations in Airborne Systems and Equipment Certification.
A.2.4 RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware.
A.2.5 RTCA/DO-313, Certification Guidance For Installation Of Non-Essential, Non- Required Aircraft Cabin Systems And Equipment.